The present invention pertains to a fastener assembly, and more particularly to a fastener assembly for use in joining a composite panel or the like to a section of metal framing, as is used in the construction of large shipping containers or trailer bodies.
In the last several years, the transportation industry has moved rapidly toward the fabrication of these containers from fiberglass, reinforced polyester-plywood panels which are fastened to a metal framework. In addition, trailer truck bodies are also being constructed in a said manner.
It should be noted, that a great number of joints are required in the assembly of each container or trailer body; for example, a normal 40' trailer will require between five hundred and six hundred separate fastener assemblies or joints. As the rigidity of the resultant structure depends soley on the strength of these joints, each fastener assembly must provide a high degree of clamping force throughout the life of the container. Further the joint must be watertight so that moisture cannot enter and weaken the plywood laminate. The fastener assembly of the present invention provides the abovementioned features, and an additional insulatory faction to prevent galvanic corrosion that is not obtained with the prior art assemblies presently being used in container constructions, as will be explained in some detail hereinafter.
Consideration is now directed briefly to the prior art type of fastener assembly used in container construction. In this regard, these assemblies normally employ a bolt member having an externally threaded elongate shank portion, a nut member having an internally threaded elongate sleeve portion; each of said members having an enlarged head portion. The shank and sleeve portions of the members are coaxially engaged in a through bore formed in the frame and panel sections in order to bring said sections into clamping engagement. The external enlarged head portion, which bears against the metal frame section, is generally provided with a deformable gasket to render the joint impervious to the influx of moisture which would otherwise impregnate the composite panel and weaken the joint. A typical prior art fastener assembly is illustrated in U.S. Pat. No. 4,033,243.
While the prior art types of fastener assemblies have been used extensively, they are possessed of a number of inherent disadvantages that are overcome by the present invention. For example, the frame sections described herein are generally constructed of aluminum or aluminum alloy. The fastener assemblies, in order to afford strength and resist the forces of tortional loading, are manufactured from steel or other ferrous alloy. As the use of conventional ferrous fasteners to secure aluminum frames results in contact between dissimilar metals which are constantly exposed to rain, road salt or the like, the resultant galvanic corrosion will eventually weaken the joint by a reduction of the bearing surfaces thereof. In addition, as the metal corrodes, capillary passageways may develop whereby water and contained corrosive ions permeate the bore to accelerate the corrosion and further weaken the plywood panel.
Some prior art assemblies attempt to avoid this corrosion by use of aluminum fasteners, but aluminum fasteners of appropriate size are unable to withstand the forces applied to the joint and are susceptible to failure within a short period of time. Non-metallic washers which cause the head portion of the fastener to stand clear of the frame section fail to isolate the shaft portion of the fastener from the through bore formed in the frame and thus allow hidden corrosion within the joint. When this corrosion extends past the external washer, the waterproof seal is broken allowing moisture to further extend the galvanic action and weaken the plywood laminate.
The present invention not only provides a strong moistureproof joint, but does so in a manner which overcomes the above-discussed disadvantages of the prior art assemblies. That is to say, the present invention provides a strong moistureproof joint which will not weaken in service due to galvanic corrosion.
Briefly, the fastener assembly of the present invention achieves the above-discussed advantages due to its unique construction. In this regard, it should be noted that there is provided a fastener assembly having an external enlarged head portion containing a novel annular groove means adapted for extruding a specially constructed annular gasket member both axially to isolate the elongate portion from the through bore, and radially to insulate the external head portion from the surface of the frame section. The gasket member and nut member are constructed such that the elongate portion of the fastener assembly is easily centered in the through bore.
The bolt member and nut member of the fastener assembly preferably each contain drive recesses for engagement by a standard power driven wrench or the like. However, conventional enlarged head configurations having multisided head portions for receiving a suitable wrench may be used.
Numerous other advantages of the present invention will become more apparent from the detailed description of the illustrated embodiment and the accompanying drawings.